Central casting couldn’t produce a better illustration of what’s wrong with the death penalty than Marvin Wilson, the 53-year-old Texan with an IQ of 61 who is (barring an unforeseen stay) scheduled for execution this evening. With the mental age of a 6-year-old, he reportedly had trouble mastering basic self-care skills like tying his shoes and counting change. His alleged role in the kidnapping and murder of police drug informant Jerry Williams was always unclear; no evidence or eyewitness reports directly linked him to the murder, and his alleged co-conspirator, Terry Lewis, escaped with a life sentence (with parole) when his wife testified that Wilson had confessed the crime to her.

Yet, the focus on extreme cases like Wilson’s — and whether he is legally and somehow “legitimately” executable despite his mental incapacity — prevents us from facing a larger truth that all state-sanctioned executions are a shameful relic of a bygone era along with the burning of witches and the use of child labor in mines.

In nearly every way, we live in a more civilized and less violent world, with dramatic declines in homicide, rape, assault, child abuse, animal cruelty and discrimination against the vulnerable. We have also acquired an ever greater understanding of the biological and social determinants of crime. Paradoxically, we tie ourselves in knots with this newfound sophistication, searching for a mythical sharp line where mitigating factors may or may not justify a death sentence. Does a brain injury from child abuse suffice? What about a parentless teenager who was led astray by a sociopath? What about a schizophrenic whose paranoia resulted in refusing to take his medications? Poverty? Retardation? Autism?

But these mental gymnastics are morally and logically bankrupt, and we cheapen ourselves by deploying them. Our eye-for-an-eye approach to the death penalty is getting progressively harder to support with reason. We know the death penalty doesn’t deter people. We know it is extremely expensive to apply “fairly.” So the only remaining arguments are emotional — the most compelling of which is that the families of murder victims want it.

Interestingly, the “closure” defense of the death penalty only gained traction in the early 1990s when deterrence arguments came up short and states found it increasingly difficult to bear the costs. Yet, defending the death penalty out of revenge or sensitivity to the victims’ families does a disservice to the many families who do not want this kind of justice. “It’s almost like if you really loved the person who was killed, you should seek the death penalty,” Kate Lowenstein, program staff at Murder Victims’ Families for Human Rights (and the daughter of a murdered father), explained to TIME.

Moreover, many of the people who witnessed the execution of a loved one’s murderer have stated that it failed to give them the closure they were looking for. This shouldn’t surprise us given renowned Harvard psychologist Dan Gilbert’s research on “affective forecasting,” and specifically the striking inability of most people to accurately anticipate their future emotional states. People think something will make them happy; but we are actually not very good at forecasting our response to even common experiences.

One of the hallmarks of a civilized society is the delegation of justice to a third party rather than to a vengeful mob with flaming torches. It’s true that support for the death penalty remains higher (around two-thirds of the population) than in 1966 (42%) when the death penalty was illegal. This puts us in the dubious company of rogue states like Yemen, Pakistan and Syria. But it’s also true that just because the majority wants it does not mean it is correct. We cheapen our government — and ultimately ourselves — by requiring the state to have a hand in what Supreme Court Justice Harry Blackmun once called the “machinery of death.”

We can keep “tinkering” with the practice of executions, as Blackmun noted, keeping Marvin Wilson alive for a few more years while we kill a more obviously despicable person, all in the hope that we can keep our hands clean. We can’t.